The invention relates to an apparatus for soldering workpieces, and preferably for soldering circuit boards and substrates which are equipped with electronic chips and/or micro components and/or sub-assemblies comprised thereof, the apparatus comprising a main solder bath, or at least a main solder wave, having a surface with which the workpiece is brought into contact.
For workpieces with very dense component packing, such as particularly occurs with circuit boards equipped with chips and with Al.sub.2 O.sub.3 substrates the problem exits, both with wave and bath soldering, that all the locations to be soldered must be reached by the solder in the required manner.
As a result of capillary action, and of the flux inclusions and the air pockets which form due to the close arrangement of the components, and also as a result of inadequate adhesive action of the relatively small area solder support points, the wetting of the areas to be soldered with the passive or mobile solder is either not possible or only very inadequate when using the previously known methods.
The wetting is made more difficult by the alloys increasingly used for surface coatings on the substrates and on the components, which are often compounds of nickel or palladium.
It is already known to provide the main solder wave with a specified structure by using a control plate (German laying open prints DE-OS No. 24 58 203 and DE-OS No. 24 55 629). Attempts have also been made to allow several soldering waves to act one after the other on the lower side of a workpiece which is moved over the waves (East German patent specification DD-PS No. 134 437, European patent publication No. 55323). All these known arrangements do not however solve the problem that with dense component packing non-soldered passages regularly occur due to inclusions of air or flux.
The problem underlying the present invention is thus to provide an apparatus for soldering workpieces of the initially named kind with which even closely packed circuit boards can be soldered without problem and with complete wetting of all the locations to be soldered.
In order to solve this problem the invention envisages that the surface of the main solder bath, or of the main solder wave should have at least one outwardly projecting lobe.